The present invention relates to motor vehicle transmission sensors.
Modem motor vehicles are equipped with numerous sensors which provide detailed information regarding the operation of the vehicle. This information may be displayed for a driver or it may be processed and provided to various vehicle control systems. For example, some transmission mounted speed sensors sense a rotating target wheel installed in the transmission and output a signal representing the angular velocity of the target wheel in revolutions per minute (rpm).
Based on the size of the target wheel and the geometry of the vehicle drive train assembly, including the transmission gearing, the drive shaft gearing, the size of the wheels, etc., the rpm of the target wheel can be processed to determine the linear velocity of the vehicle. The velocity may then be displayed to the driver via a speedometer or it may be used by a vehicle speed control system, e.g., a cruise control system, to control the speed of the vehicle.
It happens that some transmission mounted speed sensors are installed such that they protrude through a bore in the transmission housing into the interior of the housing. The bore may be formed with internal threads that engage external threads formed by the sensor housing. This allows the sensor to be screwed into the transmission housing. Alternatively, the sensor may be held in place by a bracket that is otherwise bolted to the transmission housing. The present invention understands that in either situation, the speed sensor is installed in the transmission housing by hand, which increases the production time and cost of the vehicle.
The present invention also understands that when the speed sensor is installed in the transmission it must be spaced from the target wheel a predetermined distance in order to property sense the rotating target wheel. Typically, after the sensor is installed, the gap between the sensor and the target wheel is adjusted by hand, which also increases the production time and cost of the vehicle.
In light of the above problems, the present invention recognizes a need for a transmission mounted sensor which is self retaining and can be installed so that it automatically is spaced from the target wheel a predetermined distance.
A self-retaining sensor for use in a vehicle transmission includes a sensor housing and a retaining ring extending radially from the sensor housing. The retaining ring engages an inner wall of a bore formed in a transmission housing to hold the sensor within the transmission housing.
In a presently preferred embodiment, the sensor housing defines a distal end and the sensor includes a target wheel slightly distanced from the distal end of the sensor housing. The target wheel includes a plurality of teeth. Preferably, the retaining ring is insert molded in the sensor housing and a flange extends radially from the sensor housing. Also in a preferred embodiment, the sensor housing defines a proximal end and the sensor includes a connector housing that extends from the proximal end of the sensor housing. Preferably, the connector housing is sized and shaped to receive a complementarily sized and shaped connector from a vehicle control system or a display.
In a preferred embodiment, the flange is near the middle of the sensor housing and the retaining ring extends radially from the flange. The bore formed in the transmission housing comprises a first portion, a second portion and a sensor contact face therebetween. Preferably, the diameter of the first portion is slightly larger than the diameter of the sensor housing and the diameter of the second portion is slightly smaller than the diameter of the retaining ring. The sensor is installed in the bore so that the flange contacts the sensor contact face and the retaining ring engages the inner wall of the second portion of the bore.
In another aspect of the present invention, the flange extends radially around the proximal end of the sensor body and the retaining ring extends radially from the sensor body beneath the flange. In this aspect of the present invention, the diameter of the bore is slightly larger than the diameter of the flange and the diameter of the bore is slightly smaller than the diameter of the retaining ring. The retaining ring engages the inner wall of the bore when the sensor is disposed within the bore.
Additionally, in this aspect of the present invention, the distal end of the sensor housing includes an exterior surface that has an at least partially concave curvature and each tooth on the target wheel includes an exterior surface that has an at least partially convex curvature. As intended by this aspect of the present invention, the curvature of the exterior surface of the teeth mirrors the curvature of the exterior surface of the distal end of the sensor housing. The retaining ring includes a plurality of engagement teeth and each engagement tooth is supported by a lateral support ring. In this aspect of the present invention, the lateral support ring is temporarily deformable from a retracted position to an extended position. Accordingly, the lateral support ring moves to the extended position as the sensor is inserted in the bore in the transmission housing and remains in the extended position until the concave exterior surface of the distal end of the sensor housing makes contact with the convex exterior surface of the teeth on the target wheel and the force of insertion is released allowing the lateral support ring to return to the retracted position.
In yet another aspect of the present invention, a sensor assembly for use in a motor vehicle transmission includes a transmission housing that is formed with a bore. A self-retaining sensor, that includes a sensor housing, is disposed within the bore and the sensor is held in place by a retaining ring extending radially from the sensor. Additionally, a target wheel slightly is distanced from the sensor, and the target wheel includes a plurality of teeth.